It is no exaggeration to say that, in the eyes of the great majority, George Kennan was the most famous Russianist of our time; certainly in the United States. But he was far more than that, being the author of "containment": the doctrine that guided US foreign policy in the neutralisation of Soviet power from 1946. It is no accident that the unofficial authority on containment, the historian of American foreign policy John Gaddis of Yale, is also Kennan's official biographer; though it is deeply ironic that an overt admirer of George W Bush should have been asked to write a life of his bitterest critic.

Kennan's effortless arrogance, his dry aloofness, his perfect manners, his eloquent prose and his regal habit of pronouncing on policy suggest a blue blood or at least a Boston Brahmin. Yet his humble origins in modest Milwaukee in a house stricken by the depression were a good deal more prosaic. What's more, the death of his mother a few months after childbirth left him emotionally insecure. A man of strong and seemingly unalterable opinions, Kennan was also deeply shy, surprisingly fragile, given to glooming and bouts of illness that led to hospitalisation, and burdened with Presbyterian guilt after compulsive philandering (not least with nurses).

To his own surprise, no doubt, as a man of deeply conservative convictions, Kennan became a darling of the intellectual left. To the end a great admirer of that first American academic realist Hans Morgenthau, he turned into something of a sentimentalist on Soviet Russia after the death of Stalin, giving successors such as Khrushchev and Brezhnev the benefit of the doubt in foreign policy where previously he would have scrutinised their expressions of good will with the deepest suspicion. In large part this is to be explained by his casual indifference, if not hostility, to any and every doctrine.

To Kennan, the notion that politicians could be practising Marxist-Leninists by conviction was highly improbable. In advocating the containment of the Soviet Union from 1944 to 1946, he saw the challenge as that of stemming traditional Russian expansionist ambitions pressed by a leader who was unusual not in his ideology but in his ruthlessness. It is here that Kennan soon parted company with his compatriots in and out of government, who came to embrace the cold war as an ideological crusade in which the mobilisation of public opinion not infrequently threatened to remove control of foreign policy from the elite that Kennan epitomised.

Embracing and explaining the paradoxes that made Kennan has been Gaddis's uneasy task. The accomplished, Pulitzer-winning result tells us a good deal about postwar America. For the leaders of western Europe, the question after 1945 was how to get the Americans to heave to alongside in order to offset the Soviet threat, but not to make landfall on the continent. In that Kennan concurred. Indeed the reason why he was sidelined as a policy adviser so early on in the cold war was because he firmly believed the US commitment to the balance of power in Europe should remain conditional, offshore and serving strictly American reasons of state.

Yet arguably the entire history of the cold war demonstrated that the US could only conduct its foreign policy with the consent of the people, and that could be mustered only by handing over the reins of power to those Kennan believed to be unsuitable, if not, at times, grossly irresponsible. "Myths and errors are being established in the public mind more rapidly than they can be broken down," Kennan confided to his diary in 1951. "The mass media are too much for us," he concluded. That was his reaction to McCarthyism, but it was equally his reaction to the hawkish George Bush and the invasion of Iraq in 2003.

Banished from Washington under Dwight Eisenhower and Foster Dulles after the Republicans took office in January 1952, Kennan was thrown back on his own resources, stricken with the need to atone for the unexpected turn of events for which, in fact, he was not as responsible as he believed. He had suddenly shot into the firmament under Truman and Acheson; and then, like a comet, with equal speed he disappeared off into the outer darkness.

Immured in a Venetian style tower, a four-storey study atop 146 Hodge Road in the heart of white-picket-fenced Princeton, he had instead to content himself writing memoirs, reflections and lucid essays while waiting in vain for the "call" that would summon him back to the White House. He certainly missed the "real intoxication of the spirit simply from being in physical proximity of persons of high office". But to his undying frustration, instead of statesmen he was besieged by academics, seeking insights or patronage, sometimes both. "Let's have lunch sometime," was invariably the polite if unconvincing defence against such intruders visiting the Institute for Advanced Study. This unique institution of learning took him in against the advice of professional historians such as Gordon Craig and Joseph Strayer in 1956, but with enthusiastic support from Isaiah Berlin and Theodore Mommsen, and kept him on the payroll even after retirement as one of its most illustrious figures.